Naruto: Reborn as Kakuzu, the Immortal Assassin

The Sharingan—the famed dōjutsu of the Uchiha clan. It is said to perceive chakra flow in the air, analyze the intricacies of advanced taijutsu, and replicate virtually any jutsu outside of Kekkei Genkai. This incredible power has cemented the Uchiha clan's legendary status.

However, Kakuzu was confident. No matter how powerful the Sharingan might be, it could never uncover his secret of possessing five hearts. Despite his assurance, Kakuzu was in no mood to linger. The Uchiha's innate arrogance made them challenging companions, and he preferred to move on quickly.

By the riverbank, a young man with long hair and sharp, chiseled features sat atop a large stone. His bearing exuded pride and authority. Surrounding him were a group of children, each wearing the Uchiha clan's emblem on their clothing.

The children gazed at the young man with awe and excitement.

"Akira, we heard you awakened that Kekkei Genkai! Can you show us?"

"My father always says you're the best among the younger generation. We should learn from you!"

"The legendary Mangekyō Sharingan! They say only a handful in the entire clan, aside from the clan head, can awaken it."

"Akira, for the sake of our clan's strength, teach us how to unlock the Mangekyō Sharingan!"

The young man, known as Uchiha Akira, was 19 years old. Six years ago, he had watched helplessly as his father was slain by a member of the Senju clan. In that moment, twin trails of blood had streamed from his eyes. When he was later rescued, his eyes had undergone a profound transformation.

That day, Akira vowed to avenge his father with the power of his newly awakened eyes. Yet, not long after, the tides of history shifted. The Uchiha and Senju clans brokered peace, founding a new village and heralding a new era.

In the face of this collective yearning for peace, Akira's resolve for vengeance began to waver.

"Enough!" Akira's voice thundered, snapping the children out of their chatter. He leapt from the stone, his sharp tone silencing the group. Startled by his sudden outburst, the children cowered, their excitement replaced by fear.

Akira sighed inwardly. He hadn't meant to lash out at them, they were just kids. He settled back onto the rock, his gaze softening as he stared into the distance.

Ever since the village's founding, Akira's heart had been conflicted. He understood the value of peace, yet it left him adrift, unsure of his purpose. Days passed in a haze of idleness, his ambitions dulled. Today's anger was merely a vent for his frustration, though scolding children was far from dignified.

He waved a hand dismissively. "Fine, fine. I'll show you—but just this once."

"Really?"

"Thank you!"

The children cheered, their enthusiasm quickly returning.

Amid their excited chatter, Akira closed his eyes. Chakra flowed to his brain and concentrated in his eyes. A familiar warmth surged through them. When he reopened his eyes, the children were greeted by the sight of his Sharingan, its three tomoe spinning with intensity.

This was nothing new to them. The three-tomoe Sharingan was common enough within the clan. What they were waiting for was what came next.

"Watch carefully," Akira instructed.

The tomoe began to spin faster, merging and transforming. The children held their breath as the shape morphed into something entirely new.

"It changed!"

"Is that… the Mangekyō Sharingan?"

"What kind of pattern is this? A three-bladed shuriken?"

"You idiot, it's not a shuriken. Look closer! The tips are curved and overlapping."

"Now that you mention it… it's much more intricate than a shuriken!"

Unable to agree on the design, the children eventually abandoned the debate.

"Akira-sama," one asked eagerly, "our uncles and elders say that those who awaken the Mangekyō Sharingan gain a unique ability. What's yours?"

"This…"

Akira's face paled instantly. This was the question he dreaded most—the reason he avoided others whenever possible.

Though he had unlocked the Mangekyō, its true power remained elusive. He had sought advice from the clan head, only to be met with harsh criticism.

"Foolish boy! Blaming the peace for your inability to harness your Mangekyō's power? Stop making excuses! Return only when you can wield the power worthy of the Uchiha name!"

The memory of the clan head's scorn weighed heavily on Akira. Despite his pride in being an Uchiha and his joy at awakening the Mangekyō, he felt unworthy of the gift.

Despite so many blessings seemingly within his grasp, why couldn't he unlock the true potential of his eyes? Uchiha Akira clenched his fists tightly.

"Enough, kids. Stop asking so many questions. Focus on training and strengthening the Uchiha clan. Understood?"

"Yes!"

Hearing the young ones respond in unison, Akira allowed a smile to cross his face. With a wave of his hand, he signaled them to follow as they returned to the clan's base.

Meanwhile, under the shade of a massive tree, Kakuzu opened his eyes.

"A Mangekyō Sharingan at thirteen... impressive."

His gaze shifted to the deep azure sky. Kakuzu recalled the tales about the Uchiha clan—specifically, the conditions required to awaken the Mangekyō Sharingan.

It was said that to unlock the Mangekyō, an Uchiha must endure an overwhelming trauma: either by killing someone they deeply love with their own hands or by witnessing the death of their beloved right before their eyes. This immense emotional shock would transform into a unique chakra, pushing the Sharingan to evolve into the Mangekyō.

But Kakuzu had always found this explanation incomplete.

During the Warring States Period, where death and carnage were daily occurrences, even the Uchiha couldn't escape the constant losses of friends and family. If someone's death alone were enough to trigger the Mangekyō, wouldn't there be countless Mangekyō Sharingan users?

Kakuzu had once discussed this with Senju Momoka, asking about the Uchiha and Senju clans during that turbulent era. She told him that, as far as she could remember, only Uchiha Madara had ever awakened the Mangekyō Sharingan on the battlefield.

If more Uchiha had unlocked the Mangekyō, the balance of power would have been disastrous. Even with Hashirama Senju's immense strength, it would have been a monumental challenge to contain an army of Uchiha wielding such power.

Kakuzu deduced that while intense emotional trauma was indeed necessary, there must be another crucial factor: innate talent. Without it, no amount of grief or anguish could force the Sharingan to evolve.

In other words, every Uchiha who awakened the Mangekyō was, without exception, a prodigy.

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